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APPENDIX V
MEMORANDUM BY DR JG ADAMI, CBE MD FRS, ON ANATOMICAL AND PHYSIOLOGICAL DIFFERENCES BETWEEN THE SEXES
ANATOMICAL DIFFERENCES
In the earliest years the male child is generally larger and heavier than the female, possesses a larger and heavier skeleton, a larger, more developed musculature, and larger heart, lungs, liver and other organs.
In boys and girls between the ages of 10 and 18 there appear to be three well-marked physical differences:
(a) Rate of growth.
(b) Date of adolescence.
(c) Anatomical age.
While before puberty little or no difference is noted, after puberty - that is to say, within the Secondary School age - a fourth physical difference is noted, namely:
(d) The composition of the blood.
(a) With regard to the rate of growth, an investigation recently conducted on Glasgow children showed that, from the age of 5 to 11½, boys were slightly taller and heavier than girls. At 11½ to 13½ girls were slightly taller and heavier than boys. At 13½ boys regained their superiority, and rapidly increased it.
There have been numerous investigations upon this subject; the earlier of these are well summarised in Stanley Hall's Adolescence, chapter 1. In Health and Physique of School Children (A Greenwood; PS King, 1913) we are given the English data collected through school inspections. This is a thorough review of all the available evidence by excellent statistical methods. A recent very valuable study of children attending Public Schools in New South Wales has been made by Mr FA Mecham, Statistical Officer of the Education Department, New South Wales. Examining 216,470 children, both rural and urban, he finds that:
'The average weight for boys at 5 years of age is 40½ Ibs [18.37kg], while for girls it is 39¼ Ibs [17.80kg]. This advantage in weight is retained by the boys in a slightly greater degree until the age of 11½ years is reached. The girls then become heavier than the boys by a little over three quarters of a pound, the weight at the age being boys, 69.60 Ibs [31.57kg] and girls, 70.42 Ibs [31.94kg]. From 11½ to 15½ years the girls increase in weight over the boys every half year, the maximum increase being reached at 13½ years, where girls are shown to be 7.37 Ibs [3.34kg] heavier than the boys. At that age the average weight of a boy is shown as 83.02 Ibs [37.66kg], while for a girl it is given as 90.39 Ibs [41.00kg]. At 14 years of age girls are 5.87 Ibs [2.66kg] heavier than boys, the weights for that year being boys, 88.20 Ibs [40.00kg] and girls, 94.07 Ibs [42.67kg]. At 14½ years the girl's advantage in weight falls to 4.49 Ibs [2.04kg], while a half year later, namely, at 15, the average weight of a girl is shown as 102.97 Ibs [46.71kg], and for a boy 99-79 Ibs [45.26kg], or an advantage for the girls of 3.18 Ibs [1.44kg]. At 15½ years, when the boys become heavier than the girls, the advantage on the side of the boys is only ¼Ib [0.11kg], but at the age of 16 years a comparison of weight shows that boys are 2.04 Ibs [0.93kg] heavier than girls. A boy at 16 weighs 111.17 Ibs [50.43kg] and a girl 109.13 Ibs [49.50kg].'*
*Annual Report of the Principal Medical Officer of the Department of Education for New South Wales for 1918-19, pp. 69-70.
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The Committee have received from Dr FC Shrubsall a memorandum upon the rate of growth of boys and girls. This may be summarised as follows:
There is some evidence indicating that the maximum growth in stature occurs in early summer and weight in the autumn, but it is not clear whether these facts are truly seasonal, the increase in weight being comparable with that noted in animals prior to the period of hibernation, or whether it can be ascribed in part to the more general outdoor environment of the summer season. Children appear to pass through periods of leanness and plumpness. Stratz recognises the first period of plumpness between the ages of 1 and 4, the first lean period between 5 and 7, a second period of plumpness between 8 and 10, and a second period of leanness between 11 and 15, followed by the period of puberty. Several observers think that the onset of the second dentition is preceded by a period of rapid growth, and most observers recognise a slacking of growth in girls between 8 and 9, and in boys between 9 and 11. The rapid growth just before puberty is generally preceded by a period of slackness from 1 to 2 years. These variations in rhythm are more obvious in stature than in weight, as those in weight are more peculiarly liable to accidental aberrations. Tables of average and annual increments indicate that the prepubertal rise occurs in girls at an earlier period than in boys. Boys grow more rapidly than girls up to about 9 or 10 years of age, while girls grow faster than boys from about 10 years of age to 14 or 15. Differences in stature between the sexes are more noticeable than those in weight, chest dimensions, or cranial volume. The greater growth in the stature of girls precedes the onset of puberty, and it seems probable that the physiological changes which occur when the condition of pubescence is completely established lead to changes in the metabolism of the body especially in regard to the fixation of salts.
With reference to differences in stature, the latest full study is that by Mr Mecham in the New South Wales Report already noted, page 70:
'From 5 to 10½ years girls are shorter than boys, while from that age until 15 is reached girls are recorded as taller than boys. At the age of 5 years the average height of a boy is 42.05 inches [1.07m], while for a girl it is shown as 41.56 inches [1.06m]. This is an advantage of about half an inch [12mm] for the boys, and the boys retain this advantage until the age of 7 years is reached. From then on till 10 years the margin is reduced to about a quarter of an inch [6mm] on the side of the boys, while at 11 years the average height of both boys and girls is the same, namely, 53.64 inches [1.36m]. At 11½ years, where the girls move ahead of the boys, the margin on the girls' side is 0.32 of an inch [8mm]. From then on to 13 the advantage at each half year is about three quarters of an inch, and at 13½ years the maximum increase is shown, girls being here recorded as slightly over an inch [25.4mm] taller than boys. This advantage then declines, and at 15 years the girls are about a quarter of an inch [6mm] shorter than boys. At 16 the respective heights of boys and girls are 64.24 [1.63m] and 62.27 inches [1.58m], an advantage of almost 2 inches [5cm] for the boys.'
The Committee have received further confirmation of these results from Miss RM Fleming, of University College Aberystwyth, who for some years past has been engaged in measuring, at intervals of a year, school children (boys and girls), she being a school teacher and thoroughly conversant with school conditions. She calls attention more particularly to the increase of cephalic index with growth and to the fact that, in early stages, this tendency is more marked in girls than in boys. Miss Fleming notes that her observations upon the growth of the head tally with Professor Pryor's studies of X-ray photographs of the bones of the hand, which show that in the progressive ossification a girl of 8½ has reached the
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same stage of development as a boy of 10.* She notes that changes in the head form are very slight or altogether absent in girls of 16 years onwards, whereas they continue to be marked in boys till maturity. From 3 to 8 years of age the girls' increase in cephalic index was marked, but from 9 years onwards it was not nearly so noticeable. From 3 to 10 years of age the boys did not show much increase in cephalic index, but from the age of 10 onwards the boys' average increase much exceeded that of the girls, going on rapidly until maturity.
(b) Adolescence in girls is, as a rule, earlier by one year or two than in boys.
The results of recent researches with regard to the physical phenomena of pubescence seem to indicate that the physiological age of many pupils is not in direct relation to their chronological age, and that stature and weight vary directly with the physiological age in a much closer relation than with the chronological age. Girls and boys who pass rapidly through the stages of pubescence and grow most rapidly are subjected to the greatest strain in the accommodation of their circulation to the new conditions, and need more careful supervision for the time being in mental and physical work. Such supervision is even more necessary for girls than for boys. In general, in comparing boys with girls, it may be noted that the girl is proportionately almost adult while the boy is still adolescent, and that the initial periods of strain fall at different periods. The various curves of growth obtainable from massed statistics seem to point to the fact that attention should be paid to the physiological rather than to the chronological age, and that during the periods of rapid growth, whether seasonal or due to the onset of pubescence, the strain should be lightened as much as possible.
(c) Anatomical age, as shown by teeth, nails, hair etc seems to indicate that girls are developed in advance of boys to the extent of about six months at 5 years of age and of two and a half years at the age of 15.
(d) The fourth difference has been widely studied. This, however, only shows itself after puberty, in other words, only in the latter years of Secondary School life. Up to the age of puberty little distinction has been detected in the composition of the blood of the growing boy and girl, either in the number of red and white corpuscles, the amount of haemoglobin, or the specific gravity. After puberty a definite distinction manifests itself. The observations regarding these differences have been summarised by Havelock Ellis.† According to him, Denis was the first to draw attention to the fact that there are sexual differences in the blood. His observations were confirmed by Lecanu, Becquerel and Rodier, who showed that the blood of man contains less water and more red corpuscles, and is consequently of a higher specific gravity than that of women. Cadet and Korniloff found that the red blood corpuscles in men average 5,200,000 per cubic millimetre as compared with 4,900,000 in women. Other observers have obtained closely concordant results, thus:
| Men | Women |
Welcker | 5,000,000 | 4,500,000 |
Laache | 4,970,000 | 4,430,000 |
Macphai | 5,075,000 | 4,676,000 |
Ehrmann and Siegel | 5,560,000 | 5,000,000 |
Otto | 4,990,000 | 4,580,000 |
*cf. The Development of the Bones in Early Life by Prof. T Morgan Rotch, of Harvard, and Prof. JW Pryor's article, Some Observations on the Ossification of the Bones of the Hand (Bulletin of University of Kentucky, vol. viii. No. 11, Nov. 1916).
†Havelock Ellis: Man and Woman 5th edition, London, 1914, pp 266-270. (Walter Scott Publishing Co.), cf. Leichtenstern Untersuchungen uber den Hamoglobingehelt des Blutes Leipzig, 1878)
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As regards the amount of haemoglobin, Leichtenstern found the average amount in women from the age of 11 to 50 was 8 per cent less than in men of the same life-period. McKendrick found an average of 14.5 per cent of haemoglobin in the blood of men, as compared with 13.3 per cent in the blood of women, or a difference of just under 9 per cent (14.5 : 13.3 = 100 : 91.03). As regards the specific gravity, Lloyd Jones, in his very full study of 15,000 persons of both sexes, found that the specific gravity of the blood is the same in both sexes up to the age of 15. The specific gravity in women rises up to the 14th year, when it averages 1055.5. In men, the specific gravity continues to rise until the age of 17, when it averages 1058. There is a definite reduction in women after puberty, so that the specific gravity is lower at 17 than it is at 14, and between the ages of 17 and 45 it remains about three points lower than it is in men. In other words, the blood of women is thinner than that of men; they reach the threshold of anaemia more easily.
At birth, save for the organs of generation, there may be little to distinguish the child of one sex from that of the other, but progressively during childhood up to puberty, the secondary sexual characters become more and more manifest - extent and distribution of hair, conformation of the pelvis and other skeletal parts, and so of the body in general development, or otherwise, of the mammae and of the larynx and vocal chords etc.
But while this is the case, minute microscopic study of the various organs in the two sexes (the essential organs of sex being excepted) demonstrates that the differences are quantitative, not qualitative. There appear to be no differences in the anatomy of the brain and special senses in the two sexes. At most the average brain of the males of any branch of the human race is larger than the average brain of the females of that branch. This greater average size of the brain, while closely associated with the larger size of the body, carries with it the possibility that the male in general is more generously supplied with cortical nerve cells and co-ordinating fibrils - i.e. with the apparatus of intellect. There appears, however, to be no positive demonstration either that this is the case, or that, per contra, there is a greater amount of 'padding' in the grey matter of the male brain.
Yet even if we admit the larger size of the brain as a whole in the male and admit, further, that correlated with this larger size there are more abundant nerve cells, this does not permit us to come to any definite conclusions. For much of the activity of the brain is associated with such processes as the co-ordination and control of muscular movement - with processes which are non-intellectual. We should have to prove in the first place the existence, whether localised or diffused, of a special intellectual apparatus, and that this is more fully developed in the male than in the female. This with our present knowledge - or ignorance - we have not accomplished, and as it is a matter of common knowledge that a man may be athletic with remarkable co-ordination of his muscles, with equally remarkable control of his emotions and with his special senses well developed, and that he may yet show little intellectual capacity, it is obvious that we are not in a position to decide from anatomical considerations that the average male is potentially more intellectual than the average female.
PHYSIOLOGICAL CONSIDERATIONS
If the essential organs of sex either (a) fail to develop or (b) be removed in early life, the individual tends to assume an intermediate or neutral state, the secondary sexual characters peculiar to the one or other sex failing to develop, or reverting towards those of the other sex. Obviously the development of these secondary sexual characters is bound up with the presence and function of the ovaries and testes. These organs are not merely foci or receptacles in which the primordial germ cells are lodged and undergo that succession of changes which lead to the eventual production and liberation of mature ova or sperm cells respectively, but,
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associated with that succession, these essential organs of sex exert a profound influence upon the body in general. The investigations of the last thirty years have led physiologists to the conviction that this influence is exerted not primarily through the nervous system, but through the agency of an internal secretion which differs in its properties in the two sexes. It is unnecessary here to enter into the vexed question as to the particular cells (e.g. the genital cells proper or the interstitial cells) responsible for these internal secretions of the ovary and testes respectively. There is ample evidence of the existence of these secretions, and, indeed, that the ovary, according to circumstances, is capable of giving origin to more than one. For example, the cells of the Graaffian follicle, i.e. the cells surrounding the matured ovum, when the latter escapes and becomes fertilised, yield a secretion which is essential for the proper attachment of the fertilised ovum in the uterus. It is clear that throughout life both ovary and testes elaborate and discharge into the surrounding lymph, and so eventually into the blood stream a substance or substances which, carried to other parts of the body, modify the growth and activities of the other tissues and organs, and exert a more selective influence upon those tissues and organs concerned in the production of the secondary sexual characters.
That even in the womb these interstitial cells (or the immature seminal tubes) are active and affect the rest of the organism has been demonstrated convincingly by Lillie,* in his remarkable studies upon the origin of the 'Free Martin' in cattle. The cow may cast twin bull calves, or twin cow calves and either set of twins undergo a normal development. But where it casts one bull and one cow calf, while the former develops into a fully fertile animal it has been noted for generations that the latter may grow into a kind of imperfect steer - a 'Free Martin' - with bodily conformation approximating towards that of a bull, and complete sterility. As John Hunter pointed out, its sexual organs are of the female type, with atrophy of the ovaries. Now Lillie has given the explanation. If the placentas remain distinct there are born two normal calves, male and female. If, however, they are in close apposition, that of the more active male, growing more rapidly, impinges upon and invades the territory of the other, the chorionic vessels anastomose, and the more powerfully beating heart of the male foetus forces its blood into the vessels of the female, and the bloods thus become mingled. In the male the testis with its interstitial tissue develops first and evidently produces an internal secretion before the ovary becomes active. In this way the female comes under the influence of the male hormones, and not merely is differentiation in the ovary arrested, but in place of developing ova there may appear imperfect sperm tubules, while coincidentally the secondary sexual characters approximate to the male type.
The ovaries and testes are, however, not the only endocrine glands, glands, that is to say, providing an internal secretion that affects the bodily metabolism. There is another group embracing the thyroid, thymus, the pituitary, the pineal and the adrenals, all of which are materially affected by the state of the sexual glands proper, and themselves through their secretions exercise very material influence on the activities of the sexual glands and, either directly or indirectly, on the secondary sexual organs. The physiologists of today are engaged in disentangling the relationships and mutual activities of this group. This is definitely established that there is a curiously intimate relationship between the ovaries and the thyroid. Maturation of the ova and the resultant menstruation is seen to be accompanied by enlargement of the thyroid, so also in pregnancy the thyroid undergoes swelling, while contrariwise atrophy of the thyroid is seen to be accompanied by arrest of the genital functions, delayed puberty, irregularity and arrest of menstruation, amenorrhoea, sterility etc. On the other hand, hyperthyroidism and excessive thyroid
*Lillie FB: Journal Experim. Zoology 23, 1917, 371.
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secretion may affect the genital functions in two ways. There is a condition of hyperthyroidism (often entailing mental and emotional symptoms) which produces or accompanies excessive menstruation, most often seen in girls about puberty. In the years immediately following upon the war, in several districts in England medical men have commented upon the increased frequency of 'Rossetti' necks in young women - of necks swollen so as to have a convex outline from above downwards in front, owing to enlargement of the thyroid gland.
But with true exophthalmic goitre, the opposite condition of amenorrhoea is most often encountered. Early cases, according to Dr Blair Bell, may exhibit menorrhagia (excessive and prolonged menstrual discharge), and undoubtedly in some advanced cases the metabolism is so gravely disturbed and the discharge of calcium through the urine is so persistently increased that this in itself may remove the stimulus for more abundant or more frequent menstruation.
These facts are mentioned in order to emphasise the intimate association in the female between ovarian and thyroid activity. It is comparatively rare to encounter thyroid disorders of the same type in the male. There appears in man to be closer association between the testes and the adrenals. Attention was first called prominently to this relation between the cortex of the adrenal glands and maleness by Professor Bulloch and Dr Sequiera, of the London Hospital, in a classical paper published in 1905.* Since then our knowledge of the subject has materially advanced, and as Professor Ernest Glynn, of Liverpool, summarising the evidence,† points out, whereas hyperplasia (overgrowth) of the cortex of the adrenals, or tumours originating from the same have no effect upon the secondary sexual characters of the adult male, in the male child such overgrowth or new growth is found in cases of 'Infant Hercules'. Boys so affected show precocious growth, with either obesity or great muscular development, growth of hair on face and body as in the adult male, and extreme development of the external genitalia. The striking fact is that like conditions of the adrenals (i) in young girls is associated with precocious growth and 'pseud-hermaphroditism', the bodily conformation, hairiness and overgrowth of the external genitals all approximating to the male type; (ii) in adult women before the menopause, the breasts atrophy, as do also the uterus and ovaries, hair develops on the upper lip and face, with, often, deepening of the voice. The most remarkable case is one which Dr Gordon Holmes has permitted Professor Glynn to publish, in which a girl of 24 had been normal in appearance and History until the age of 19. Then menstruation ceased. At 20 she had a beard and moustache. Three years later she was noted as thinner and flat-chested, with increase of hair upon her limbs, atrophy of uterus etc. In this year a large tumour was removed from between the liver and kidneys. Sections sent to Professor Glynn showed this to be a tumour of the adrenal cortex. Following upon the operation menstruation returned, the hair disappeared from the face, the figure became characteristically female, and she regained all the attributes of a modest woman. I purposely give these details at some length, inasmuch as I find that thus far this evidence of the differences in the interrelationship between the organs of the internal secretions and the essential and secondary organs of sex is scarcely known outside the medical profession. Obviously it has a profound bearing upon the problem before the Committee. Others associate the pituitary, or hypophysis cerebri, with masculine characters, deficiency of the anterior portion being often found associated with a more rounded feminine contour of the body and the feminine disposition of bodily hairiness, while its overgrowth has been found associated with virility. The evidence, anatomical and experimental, of such relationship, while striking, is still small in amount. The same is true as regarding the pineal gland.
*Bulloch and Sequiera: Trans. Path. Soc. London, 56, 1905, 189.
†Glynn: E. Journal of Obstetrics and Gynaecology of the British Empire Spring Number, 1921, p. 44.
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This relationship between the ovaries and the thyroid appears to be of peculiar significance in respect to the calcium metabolism of the body. The part that calcium (lime) and its salts play in the proper functioning of the body is being more and more brought home to us. It is realised today that they are necessary for much more than the proper formation of bone, that they are necessary for the activity of certain important ferments, that they play a part in maintaining the blood pressure, that, as Ringer and Buxton showed years ago, they control the excitability of muscle. From these and other observations on the neutralising action of calcium upon the excitability of muscle induced by potassium and other salts, MacCallum and Voegtlin* were led to test the effects of calcium salts upon experimentally produced tetany. Tetany is a state of convulsive excitability of the muscles which may be set up by several causes, and can experimentally be produced by removing the minute parathyroid glands in man and the lower animals. They found that so long as they continued the administration of calcium for so long could they arrest and prevent the onset of tetany in these animals, observations which have been abundantly confirmed by Edmunds.† Hertz‡ also has noted that following the removal of the thyroid and parathyroids in man, the tetany which manifested itself can be prevented by the administration of parathyroid, while further, as showing the relationship between these glands and the calcium metabolism of the body, Erdheim§ has observed that in cases of osteomalacia, in which there is great loss of calcium from the system with pronounced softening of the bones, the parathyroids are found diseased (hypertrophied). More recently Noel Paton and his pupils have shown that methylguanidin is an active factor in the production of tetany, and that this substance is normally destroyed by the parathyroids, and in so doing has thrown doubt upon the part played by calcium deficiency in the development of this condition.|| While these observers point out that after removal of the parathyroids, methylguanidin accumulates in the body and makes an appearance in the urine, they have not, however, proved either that methylguanidin is the constant and essential cause of tetany or that the parathyroids play no part in the calcium equilibrium of the body. Clinical evidence, indeed, is strongly in favour of this latter view, and within the last few weeks Vines, who previously had, with Blair Bell, laid stress upon the fact that the calcium of the blood is present in two forms, ionised and unionised, studying certain cases of chronic ulceration has shown that in these there is a distinct lowering of the ionised calcium of the blood (from a normal 10.7 mg per cent to 6 and even 4.83), and by the exhibition of parathyroid gland substance he has raised the amount to the normal and at the same time brought about healing of the ulcers.¶
Blair Bell** has carried the matter further, and has laid down as the results of his studies that there is an important difference between the male and the female, showing itself with the onset of puberty, namely, that in the female the calcium metabolism becomes unstable, whereas in the male it remains relatively constant. Objection has been taken to his microchemical method on the ground that it is wanting in quantitative exactitude. These objections would be valid were the differences recorded minute, but, according to Blair Bell, they are too great to be explained
*MacCallum and Voegtlin: Bull. Johns Hopkins Hospital 19, 1908, 91.
†Edmunds: Jour. of Path and Bact 16, 1912, 481; 18, 1913, 5; and 21, 1916, 23.
‡Hertz: Guy's Hospital Reports 67, 1913, 153.
§Erdheim: Akad. d. Wissensch. Math. Naturwiss. Kl. Wien 116, 1907, Heft 3, 311.
||Paton, Findlay and Burn: Guanidin (and methylguanidin) and Tetany, Jour. of Physiol 17, 1915, xvii.
¶Grove and Vines: British Med. Journal 1921, ii., 687.
**Blair Bell: The Sex Complex 2nd edition, London, 1921. For details of his method see British Med. Journal 1909, I., 517, 592, 6.55.
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by errors of observation. He suggested that the method shows the presence of calcium in an ionised form.
He finds that both the thyroids and ovaries (the latter in their periods of functional activity) promote the discharge of calcium from the system, whereas the adrenals, the pituitary and the parathyroids favour its retention. He finds in the normal woman a periodic reduction in the circulating calcium, followed by a gradual rise; there is a distinct ebb and flow. I have consulted several leading physiologists upon this point, and find that there is widespread doubt regarding Dr Blair Bell's 'ebb and flow' doctrine based upon the inaccuracy of his micro-chemical method. Blair Bell's observations were made at a time when the finer methods of determination of calcium in the blood had not been developed. As GW Clarke* points out, certain of the methods in frequent use today are far from perfect. The most thorough, that of ashing with platinum, is laborious and time-consuming, and he concludes that, after all, a modification of the direct precipitation method employed by Blair Bell, with permanganate titration is accurate to approximately 2 per cent, the values agreeing well with those obtained by the platinum method.†
The only observers, to my knowledge, who have made studies along Blair Bell's lines are, on the one hand, Meigs, Blatterwick and Carey,‡ who, in cows, found the calcium of the serum practically constant during pregnancy and lactation, and, on the other hand, Kehrer,§ who, employing an ashing method, found a definite fall in the calcium of the whole blood of women during the latter half of pregnancy, and particularly low values in cases of eclampsia complicating pregnancy, and Kehrer appears to have employed the more accurate method. But no one, apparently, has repeated the observations upon the existence or non-existence of a periodic calcium tide in woman. What has been shown by many observers is that in health the calcium of the blood remains remarkably constant, the amount varying from 9.3 to 11 mgm [mg] per 100 cubic centimetres of serum. While, on the one hand, we recognise the existence of a large store of calcium in the bones which, in the case of loss of calcium in the blood, might be expected to restore the balance with relative rapidity, on the other hand we have abundant clinical evidence that, in certain conditions of disease (tetany of various orders, eclampsia, chronic ulceration (Vines) and certain forms of nephritis), there may be definite lowering of the calcium content of the fluid of the blood. It is thus not impossible that during the menstrual period there may be a transient lowering of serum calcium. But, admittedly, Blair Bell's observations need confirmation by the more precise methods of blood analysis which are at our disposal today.
I am prepared to find, further, that during lactation the blood yields some evidence of the heavy call upon the calcium of the blood and of the body in general. It has been calculated that the calcium contained in an ounce [31g] (two tablespoonfuls) of milk is equivalent to a dose of five grains of calcium lactate.
This at least is significant; that the condition of osteomalacia or extreme softening of the bones as a general, as distinct from a local, condition, is almost entirely confined to the female sex, frequently in associa-
*Clarke GW: Journal of Biol. Chemistry 1921, 49, 487.
†What appear to be yet more delicate methods, suitable for the detection of calcium in small quantities of serum, have been published by Kramer and Tisdall (Journal of Biol. Chemistry 1921, 47, 475) and by Laidlaw and Payne (Biochemical Journal 1922, 16, 494). The latter appears to be particularly delicate.
‡Meigs, Blatterwick and Carey: Ibid 1919, 37, 1.
§Kehrer: Archiv. fur Gynakologie 1920, 112, 487.
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tion with rapidly recurring pregnancies; it is rare in the man. And some cases have been arrested by removal of the ovaries.*
To a slighter drain or defective calcium metabolism must probably be ascribed that lesser grade of softening of the bones leading to spinal curvature and postural defects, so common in girl pupils, so relatively uncommon among boys. To a deficiency in calcium may also be ascribed, at least in part, the greater nervous excitability of the female.
PHYSIO-PSYCHOLOGICAL CONSIDERATIONS
Bearing these data in mind, we can now approach the problem of the psychological differences between the sexes.
It has already been pointed out that anatomically, save in the matter of average size of brain (and spinal cord), there is no difference that has thus far been determined.
Have we any evidence that the nervous system is affected in its function directly or indirectly by the endocrine activities of the essential organs of sex, and that in this way any different trend may be given to the cerebral functions in the two sexes?
The very fact that with atrophy or removal of the ovaries before or during the period of sexual activity there is developed not merely a coarser and more masculine skin, and more masculine voice, but also a more masculine - or less feminine - loss of reserve and approximation towards a masculine bluntness of speech, is clear evidence that the ovaries have an influence upon the mental state. The same is true regarding the mental characteristics of the eunuch, who exhibits a lack of those mental qualities which we denominate virile. But whether the action of the genital hormones is direct upon the nervous system, or indirect through stimulation of other endocrine glands to increased excretion, is not as yet determined. We know, for example, that the secretion of the adrenals has a striking effect upon the sympathetic nervous system, and that hyperthyroidism is accompanied by a train of changes in the nervous state of the individual, characterised by tremors, tearfulness, and a heightened emotional state. We have still to determine whether - which is quite possible - the long-continued influence of the testicular hormones acting upon the nervous system set up in the brain a different response to that exerted by the ovarian, or whether we deal rather with a summation of various responses on the part of the endocrine glands and the effects of their hormones upon the central nervous system, a summation which is different in the male from what it is in the female.
With Professor Godfrey Thomson, it may be serviceable here to quote from Punnett (Mendelism 1918, p. 208):
'Effective mental ability is largely a matter of temperament, and this in turn is quite possibly dependent upon the various secretions produced by the different tissues of the body. Similar nervous systems associated with different livers might conceivably result in individuals upon whose mental ability the world would pass a very different judgement. Indeed, it is not at all impossible that a particular form of mental ability may depend for its manifestations, not so much upon an essential difference in the structure of the nervous system, as upon the production by another tissue of some specific poison which causes the nervous system to react in a definite way.'
*This is not opposed to the observation previously noted, that parathyroids have been found diseased in this condition. As I pointed out many years ago, the like symptoms may be set up by over-activity of an organ supplying an internal secretion, and defective action or disease of the organ which neutralises that internal secretion or the products of its activity.
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I am indebted to Mr Burt for a helpful criticism upon the above passage, namely:
That disturbances in the endocrine glands appear to affect emotional characteristics far more than intellectual abilities, and it is in the former that the sexes seem to differ most.
The considerations here given indicate why it is that we incline to agree with some of our medical and psychological witnesses that the products of the ductless glands discharged into the blood differ in their proportions in the male and female, and that a priori here probably is to be found the clue to the inconsistencies between short laboratory experiments and the general belief that women have, in certain directions, a different kind of mental ability or emotional temperament from that exhibited by man.
It appears to be an established fact that girls in general are (i) not so strong physically as boys; (ii) are more highly strung and liable to nervous strain, which very possibly is associated with the fact that physiologically they are liable to heavier drains upon the circulating calcium of the blood; and (iii) with their thinner blood with lowered haemoglobin content, after puberty they are nearer to the threshold of anaemia.
Medical statistics indicate that there is a higher percentage among girl pupils of cases of anaemia, spinal curvature, defective eyesight and minor physical defects.
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APPENDIX VI
TIMETABLES OF A FEW SECONDARY SCHOOLS OF DIFFERENT TYPES
(Note. We have taken the latest available timetable in each instance, but it must be borne in mind that such timetables are frequently modified. The timetables show the number of hours a week devoted to each subject.)
[Note: in the printed version times are shown as hours and fractions of hours. For this online version I have translated these into hours and minutes. Thus 2¼ is shown as 2:15.]
I TIMETABLE OF A MUNICIPAL SECONDARY SCHOOL FOR BOYS AND GIRLS (i.e. a co-educational day school)
School hours: 9 am to 12.10 pm and 2.05 pm to 4.05 pm
Table I
[page 188]
II TIMETABLE OF A MUNICIPAL SECONDARY SCHOOL FOR GIRLS AND BOYS, WITH A SLIGHT TECHNICAL BIAS
School hours: 9.30 am to 1 pm and 2.30pm to 4.30pm
Table II
[page 189]
EXPLANATORY NOTE ON TABLE II
The girls have access to well fitted cookery and laundry rooms and in addition to Cookery and Laundry work they study Housewifery and Needlework.
Thus more time is assigned to Handwork subjects than is usually the case, and moreover, these subjects are taught in surroundings which bring the pupil into contact with the outside world.
All pupils take German as the first foreign language. This was determined before the war owing to the bearing of German science on the local industries (in this case mining and iron industries).
The curriculum in the first year is as follows: English, History, Geography, German, Mathematics, Physics (Introductory Science), Handwork, Drill [PE], Music, Games.
The subjects studied in the first year are continued throughout the school course with the exception that, at the beginning of the second year, Introductory Science is replaced by Chemistry (for boys) and by Botany (for girls). Differentiation begins in the second year. The better boys have a choice between Latin or Physics and the more able girls have a choice between Physics, Latin and additional Domestic Science. Only scholars with distinct literary ability are allowed to take Latin. Thus the majority study one foreign language, and, as a rule, those who take up Latin are intending candidates for an Arts Degree or for entry into profession (e.g. law, medicine).
The weaker scholars have no opportunity of studying a second foreign language; instead they devote their time to practical subjects which are potentially vocational.
III TIMETABLE OF A CO-EDUCATIONAL BOARDING SCHOOL
School hours: 9.00 am to 12.50 pm. No set hours in the afternoon.
Table III
[page 190]
IV TIMETABLE OF A COUNTY SECONDARY SCHOOL FOR BOYS
School hours: 9.35 am to 12.50 pm and 2.00pm to 4.15 pm
Table IV
[page 191]
V TIMETABLE OF A COUNTY SECONDARY SCHOOL FOR GIRLS
School hours: 9.15 am to 12.30 pm and 2.30 pm to 4.30 pm
Table V
[page 192]
VI TIMETABLE OF A HIGH SCHOOL WITH A LONG MORNING SESSION
School hours: 9.20 am to 1 pm and on Monday only 2.30pm to 3.30pm
Table VI
[page 193]
VII TIMETABLE OF A LARGE MODERN BOARDING SCHOOL FOR GIRLS
Table VII